Hashimoto's thyroiditis

Question 1

epidemiology of hashimoto’s thyroiditus

Answer 1

most common form of thyroiditis and most frequent cause of hypothyroidism in US

iodine deficiency is the most common cause of hypothyroidism worldwide

female more

all age group, most common 30-50yrs

Question 2

pathophysiology of hashimoto’s thyroiditis

Answer 2

unknown aetiology - genetic and env factors likely to play a role

immunological mechanisms:

• associations with HLA-DR3, DR4, DR5 have been proposed
• cellular (especially T cells) and humoral immune responses are activated -> active B lymphocytes produce TPO Ab and Ab against thyroglobulin (TG) –> destruction of the thyroid tissue

Question 3

associations with hashimoto’s thyroiditis

Answer 3

increased risk of non-hodgkin lymphoma usually originating from B cells

increased risk of autoimmune disease - t1dm, SLE, graves disease, addisons

Question 4

clinical features of hashimoto’s disease

Answer 4

early stage

• asymptomatic
• goitre - non-tender or painless, rubbery thyroid with moderate and symettrical enlargement
• hashitoxicosis - transient hyperthyroidism due to follicular rupture of horone containing thyroid tissure –> irritability, heat intolerance, diarrhoea

late stage

• thyroid may be normal sized or small if extensive fibrosis has occured
• hypothyroidism eg cold intolerance, constipation, fatigue

Question 5

Ix for hashimoto’s disease

Answer 5

early stage transient hyperthyroidism possible - low TSH, high free T3 and 4

progression - subclinical hypothyroidism - high TSH, T3 and 4 normal

late stage - overt hypothyroidism - high TSH, low T3 4

anti-TPO +ve (high anti-microsomal Ab)

anti-Tg Ab +ve

high LDL, low HDL, low Hb

US - atrophic phenotype = reduction in thyroid size, goitrous phenotype = heterogenous enlargement

FNAC - exclude malignancy or lymphoma

radioactive iodine uptake test - variable, often patchym irregular. reduced uptake in transient hyperthyroidism

Question 6

pathology of hashimoto’s disease

Answer 6

diffuse lymphocytic inflitration (cytotoxic T lymphocytes) with germinal centre, oncocytic metaplasic cells (huryhle cells) and fibrotic tissue

Question 7

treatment of hashimoto’s

Answer 7

levothyroxine for life - start at lower and more slow acting dose with increasing severity of hypothyroidism because of risk of cardiac SE

life long monitoring - of thyroid parameters (TSH) to adjust treatment

Question 8

complications of Hashimoto’s

Answer 8

permenant hypothyroidism

myxoedema coma

thyroid lymphoma